1. Field
The present invention relates to a nonvolatile semiconductor memory device two types of memory areas provided in a single memory chip, a method of fabricating the nonvolatile semiconductor memory device, and a process of writing data of the nonvolatile semiconductor memory device.
2. Related Art
Various types of nonvolatile semiconductor memory devices have been developed according to various types of intended purposes or usages. For example, Japanese patent application publication JP-A-H10-106279 discloses a configuration that two types of memory areas are provided on a single memory chip. One of the memory areas is a binary memory area (SLC: single level cell) which is suitable for high-speed write and readout and the other is a multilevel memory area (MLC: multi level cell) which has an improved amount of data stored per memory cell.
The above-described nonvolatile semiconductor memory device includes a cell array region for a single bit operation mode, a cell array region for a multi bit operation mode, a page buffer circuit for the single bit operation mode and a page buffer circuit for the multibit operation mode all of which are provided on a single substrate. As a result, both or one of a multi-bit operation and a single-bit operation is executable simultaneously or selectively.
Thus, a using manner of each cell array region of the memory cell array is changed according to various purposes of the nonvolatile semiconductor memory device. However, when a memory cell device structure in each cell array region in the memory cell array is uniformed, there results in a case unsuitable for use of each cell array region.